1. Technical Field
The present invention relates to a sheet feeder control method for controlling a sheet feeder of an image forming apparatus, a sheet feeder for an image forming apparatus controlled by the sheet feeder control method, and an image forming apparatus equipped with the sheet feeder.
2. Related Art
In a sheet feeder of an image forming apparatus, it is common to detect the sheet feeding state by using a sheet sensor and detect a sheet jam (referred to as the jam in the present specification) on the basis of the detection result provided by the sheet sensor, such as the sheet sensor detecting no sheet within a predetermined time or continuing to detect a sheet for longer than a predetermined time.
In a typical sheet feeder, to detect the removal of the sheet remaining in the sheet feeder and return the sheet feeder to the normal state (i.e., usable state) from the jammed state, a cover of the sheet feeder for allowing the removal of the remaining sheet is first opened and then closed.
That is, whether or not a sheet remains in the sheet feeder is checked upon transition of the signal from an opening sensor that detects the opening and closing of the cover from a signal indicating the cover open state to a signal indicating the cover closed state. Then, if it is confirmed that any sheet remaining in the sheet feeder has been removed, the sheet feeder returns to the normal state from the jammed state.
However, according to this procedure, even if a sheet is stopped with most of the sheet discharged to the exterior of the sheet feeder and thus it is possible to complete an unjamming operation simply by pulling it, nevertheless an operation of opening and closing the cover is performed at least once. Such an operation is troublesome for users.
To further facilitate the unjamming operation, a mechanism may be provided that displays an instruction guide for the unjamming operation on an operation panel in accordance with detection results provided by a feed sensor and a cover opening and closing sensor, for example. Although generally successful for its intended purpose insofar as such a mechanism that presents a user with clear instructions for the unjamming operation, the mechanism does not address the issue that the process of returning the sheet feeder to the normal state involves the basically unnecessary operation of opening and closing the cover.